It is mandatorily required for glycidyl ethers of phenols utilized for electric and electronic materials that the content of hydrolyzable chlorine be small, and such has been widely recognized in the art. That is, hydrolyzable chlorine results in adverse effects such as deterioration of electrical insulation, corrosion of lead wires, etc. Particularly with glycidyl ethers of phenols as encapsulation materials for integrated circuits using semi-conductors, it is essential that the content of hydrolyzable chlorine be small. For example, in integrated circuits having an integration density of 64 killobits or more, it is required that the content of hydrolyzable chlorine be not greater than 600 ppm.
To reduce hydrolyzable chlorine, various processes for production have been studied. For example, a process of producing glycidyl ether of bisphenol A which comprises gradually feeding an aqueous solution of sodium hydroxide to a solution of bisphenol A in epichlorohydrin, wherein water is distilled off azeotropically with epichlorohydrin at low temperatures under reduced pressure and the distilled-off epichlorohydrin is circulated into the reaction system, is described in Japanese Patent Publication No. 36000/78. In the examples of the above patent publication, the content of hydrolyzable chlorine is shown to be 1200 to 4500 ppm and no sufficient improvement effect is obtained thereby. In Japanese Patent Application (OPI) Nos. 90400/79 (the term "OPI" used herein refers to an unexamined but published patent application) and in Japanese Patent Application (OPI) No. 13596/79 and U.S. Pat. No. 3,121,727, processes of producing glycidyl ethers of polyhydric phenols characterized by adding an alcohol to a solution of polyhydric phenols in epihalohydrins are described. With respect to the examples of these patent publications or patent the content of hydrolyzable chlorine in glycidyl ether of bisphenol A obtained from bisphenol A and epichlorohydrin is approximately 1000 ppm and the total chlorine content is from 1500 to 3500 ppm in the case of Japanese Patent Application (OPI) No. 90400/79; and a content of hydrolyzable chlorine in glycidyl ether of phenol novolak obtained from phenol novolak and epichlorohydrin is 1500 ppm in the case of Japanese Patent Application (OPI) No. 13596/79. Such are not sufficiently improved results, however. Further, it is mentioned in the patent publications or patent as cited above that moisture may not be removed from the reaction system. However, it is well known that epichlorohydrin is decomposed even in the co-presence of water, which is disadvantageous from the industrial viewpoint. Further, there is described in Japanese Patent Publication No. 46981/77 a process for producing glycidyl ether of phenols which comprises reacting phenols with an excess of epichlorohydrin using quaternary ammonium salts or quaternary ammonium bases as addition catalysts in a first step to prepare chlorohydrin ethers of phenols, and then adding anhydrous sodium hydroxide to effect dehydrochlorination from the chlorohydrin ether group. According to the examples of this patent publication, only glycidyl ethers of phenols having a content of hydrolyzable chlorine of 1000 ppm were produced. In Japanese Patent Application (OPI) No. 141479/80, a process of producing glycidyl ethers of phenols which comprises preparing chlorohydrin ethers of phenols from phenols and epichlorohydrin using addition catalysts such as quaternary ammonium salts or the like, removing an excess of epichlorohydrin by distillation, and then effecting dehydrochlorination using an aqueous solution of alkali metal hydroxides is described. In the examples thereof, the content of hydrolyzable chlorine in the glycidyl ethers of phenols is 700 ppm or more, and no sufficient improvement effect is obtained thereby.
It is known that in epoxidation in which glycidyl ethers of phenols are produced from phenols and epichlorohydrin, the reaction takes place in two steps. When taking phenol as an example, glycidyl ether of phenol is produced in two steps of addition reaction and cyclization reaction as described below: ##STR1##
The intermediate, 1,2-chlorohydrin ether of phenol, in part induces hydrolyzable chlorine, but this 1,2-chlorohydrin ether of phenol is easily cyclized in a subsequent purification step as defined below to convert into glycidyl ether of phenol. The term "purification step" as used herein refers to a reaction step in which the 1,2-chlorohydrin ether group is converted into the glycidyl ether group through cyclization reaction by adding sodium hydroxide to an aromatic hydrocarbon solution or ketone solution of glycidyl ethers of phenols containing a small quantity of 1,2-chlorohydrin ether of phenols obtained in the epoxidation.
The hydrolyzable chlorine which comes into question in the present invention cannot be removed by the aforesaid purification step and has the following structure in the case of phenol: ##STR2##
These hydrolyzable chlorines are impurities produced by side reactions in the epoxidation and cannot be removed by the purification step described above.
As a result of extensive investigations on attempting to obtain glycidyl ethers of phenols containing as little hydrolyzable chlorine as possible, the present inventors have reached the present invention.